PURPOSE: To polish the rugged surface and the interior of a deep groove easily and uniformly and absorb the vibrasion by rotating an abrasive sponge wheel with the abrasive cloth paper stuck on the outer periphery of a sponge disk by means of an electric grinder and bringing it into contact with the surface to be polished.

CONSTITUTION: An abrasive sponge wheel 4 is connected to the rotary shaft 6 of a portable electric grinder 5, the sponge wheel 4 is rotated at a high speed by the drive of this grinder 5, the abrasive cloth paper 3 stuck on the outer periphery of the sponge disk 1 of this sponge wheel 4 is brought into contact with the desired surface to be polished, the sponge disk 1 is deformed following the rugged surface and the interior of a deep groove, and even the rugged surface and the interior of the deep groove are uniformly polish-machined with the abrasive cloth paper 3. In addition, the vibration caused by polishing is absorbed via the elasticity of this sponge disk 1, thus the vibrasion is prevented from being transferred to the hand holding the electric grinder 5.